@BvilleBound 

The Deco does not pass the wireless password to the Verizon device it has its own network and password.

On the Windows computer forget the network so it would be as if you are connecting the first time.

If that still does not work, use the Deco app to access the Deco remotely (disable Wi-Fi), and change the network name and password to something different. Try to connect to the new network on your Windows computer.

Dear Tony:  The Deco M9 obviously passes the user's login credentials to the Verizon router.  It you are logged into the Deco M9 as your WiFi connection, then all WiFi traffic / data sent from your device (including your attempted login credentials) are (1) received by a Deco M9 in your WiFi mesh, then (2) transferred to the Verizon router and modem out to the internet.

This is evidenced by my ability to login directly to Verizon WiFi, but not via the Deco M9, when using my Windows 10 laptop.  So the login credentials work when sent directly to the Verizon router and modem, but not via the Deco M9.

Curiously, my iPhone can connect via the Deco M9 using the same login credentials. 

So the fault is clearly with the Deco M9 when used with Windows 10 PCs.  Something about the login / access sequence is failing via the Deco M9.

I spent 30 years in IT, so I understand this stuff.

Mark

@Tony 

@BvilleBound 

Please follow up with our support team if you believe that is the case so you may discuss the operation with one of our senior engineers.

Dear Tony:  As noted in my original post on this forum, I already contacted the TP-Link tech support team.  They replied quickly and provided two suggestions I am going to try.  I will let you and forum members know if one of these suggestions worsk.

Mark

@Tony 

To everyone in the TP-Link forum:

• First, a BIG Thank You to the TP-Link customer support team!  I contacted them about the Windows 10 login problem; they kindly replied quickly and offered a number of suggestions.
   
• Second, one of the suggestions worked.  I reset the password for the TP-Link Deco M9+, using the TP-Link app on my iPhone.  Voila!  I could connect to the main Deco M9+ from my Windows 10 pc.  This was because (1) The Deco M9+ password cannot be the same as your ISP's WiFi password, or (2) You must change your Deco M9+ password after you relocate your Deco mesh system to a new location with a new internet modem etc. or (3) You must change your Deco M9+ password after you reset your Deco 'master' unit.  As I suggested to the TP-Link support team, this glitch can probably be fixed with a firmware update. 

In any case, changing your Deco M9+ password is a good Step #1 if you are having trouble connecting from your PC, tablet or iPhone.

I hope this is helpful,

Mark

@BvilleBound